Pneumocystis carinii is a major pathogen of patients with HIV infection. The immune responses to P. carinii are poorly understood, but cytokines may play a role in both clearing P. carinii infection and in hypoxia associated with P. carinii pneumonia (PCP) that may be exacerbated after therapy is initiated. Collaborative studies with investigators at Indiana University continue. Based on preliminary polymerase chain reaction (PCR) studies, investigators at Indiana University are examining the potential role of interleukin-10 (IL-10) in the pathogenesis of P. carinii pneumonia using a CD4-depleted mouse model. In addition, we have completed a study with Dr. Vogel examining the effects of IL-12 in scid mice with P. carinii pneumonia. In this model no effect on PCP was seen when IL-12 was administered either at the time of P. carinii exposure or 4 weeks after exposure. It is hoped that these studies will provide insights into the role of cytokines in P. carinii pneumonia and may provide mechanisms for increasing clearance or decreasing the inflammation that may cause hypoxia.